1. Field of the Invention
The present invention relates to communications; more specifically, the updating of keys or other information used by communicating parties.
2. Description of Related Art
A typical wireless communications system provides wireless communications services to a geographic region. When a wireless unit attempts communications with the wireless communications system, the wireless communications system authenticates or verifies the wireless unit's identity before allowing the wireless unit access to the wireless communication system. To do so in a typical wireless communications system, both the wireless unit and the wireless communications system have a secret value called A-KEY. The wireless communications system uses the A-KEY and a randomly generated sequence RANDSSD to generate a shared secret data value (SSD). The SSD can be divided into SSD-A (Shared Secret Data A) and SSD-B (Shared Secret Data B) values. The SSD-A value is used for authentication procedures, and the SSD-B value is used for key generation and encryption procedures. The wireless communications system transmits the RANDSSD to the wireless unit. The wireless unit then calculates SSD in the same fashion as calculated by the wireless communications system.
Before accepting new SSD values to be used in authentication and encryption procedures, the wireless unit validates the new SSD values. To do so, the wireless unit generates a random challenge RANDBS to generates a validation signature value AUTHBS. The wireless unit also sends the RANDBS to the wireless communications system, and the wireless communications system derives AUTHBS in the same fashion using RANDBS from the wireless unit. The wireless communications system sends the AUTHBS value to the wireless unit, and the wireless unit compares the AUTHBS value generated at the wireless unit with the AUTHBS value sent from the system. If the comparison is successful, the SSD update is successful.
After the SSD update, the wireless communications system typically authenticates the wireless unit to ensure that the wireless unit has properly calculated the SSD. The wireless communications system generates a sequence, such as a random challenge RANDU, and sends the sequence RANDU to the wireless unit which uses RANDU and SSD-A to generate an authentication signature value AUTHU. The wireless communications system generates the authentication signature value AUTHU in the same fashion. The wireless unit then transmits the value AUTHU calculated by the wireless unit to the wireless communications system. The wireless communications system compares the value AUTHU calculated by the system and the AUTHU value received from the wireless unit. If the values match, the wireless unit is authenticated.
The above-described SSD update and authentication of the wireless unit requires that the wireless unit confirm the validity of the SSD update followed by the system performing a separate authentication of the wireless unit to ensure the validity of the SSD update from the perspective of the wireless unit and the wireless communications system. As a result, the wireless unit confirms that the SSD update is successful before the authentication of the wireless unit can be initiated. After the wireless unit confirms the SSD update, the system performs a separate authentication requiring the system to generate additional information, such as a random challenge RANDU, and to send the random challenge to the wireless unit. The wireless unit must then respond by sending to the system the authentication signature value AUTHU derived using RANDU.